The invention relates to systems and methods for more effectively and efficiently screening particulate material, and more particularly to these screening systems in which the structure support members therefor are more effectively and efficiently protected from wear due to engagement by the particulate material during the screening operation.
Screening is the separation of aggregate particles into various sizes. Various conventional types of screens are used to separate aggregate including vibrating inclined screens, stationery inclined screens, vibrating grizzly screens, vibrating horizontal screens, rotary screens and static screens.
The vibrating inclined screen is the most popular of the screen types. Types of vibrating screens include those with two and four bearings, high speed screens, and screens which vibrate at the natural frequency of selected spring clusters. The majority of aggregate producers utilize a two or three deck vibrating screen with two bearings. The two bearing, circle throw, inclined screen utilizes a counter weight on a shaft to move the screen through approximately a 3/8 inch displacement throw. Screen throw varies inversely with the shaft speed with typical ranges from 800 to 950 rpm. The screen is isolated on springs and is customarily powered by an electric motor with a V-belt drive. Screen slopes vary from 15.degree. to 30.degree. for dry separations to slightly flatter for wet sieving.
The included vibrating screen is angularly adjustable to an inclined position to improved efficiency. Variations in slope, speed, stroke, and direction of rotation provide the flexibility required to determine the best combination of variables for making the separation. The inclined vibrating screen is typically used for aggregate separation. The addition of extra counterweights allow the screen to handle dense, coarse aggregate. When properly sized, the inclined vibrating screen performs virtually maintenance-free except for wear from the aggregate as it is processed. Horizontal screens are normally selected when conserving headroom or there is a need to maintain a lower profile. Variations in speed and stroke can be made for a given separation scheme.
The screening surface used in combination with a given vibrating screen must be strong enough to support the weight of the material, flexible enough to withstand the vibration, and provide enough open area to allow the desired throughput of aggregate. Various conventional screening decks and screening elements are known for this purpose.
The metal frame member system is designed to attach to the interior support members of a vibrating screen box. The vibrating screening boxes comprise a pair of vertically-extending sidewall members disposed in a vertical position in a parallel vertical plane. The rear vertically-extending edges of the sidewall members are joined one to the other by a vertically-extending rearwall member. The vibrating screening boxes are also held together by interior metal support members joined to the sidewalls and rearwall thereof. The metal frame member system which is non-integral is designed to attach to the metal support frame members. Once the metal frame system is in place attached to the interior of the vibrating screen box, the screening process can be conducted.
The above-described screen systems has a number of drawbacks. For example, the use of metal frame members causes several further problems. One of these problems is that they suffer from a substantial wear problem which results from impact and frictional engagement caused by the flow of aggregate material during the screening process. However, present commercially available systems for overcoming this wear problem do so at the expense of (a) extremely high replacement costs for the replacement materials and labor, and (b) extensive production downtime for completing the replacement process.
Accordingly, the need remains for a system which is low cost, fast, and convenient, which permits the effective and efficient replacement of screening system thereby avoiding excessive downtime, and, which substantially reduces the wear problems associated with the metal frame members.